1. Field of the Invention
Embodiments of the invention relate to a display device having touch sensors and a method for driving the same.
2. Discussion of the Related Art
A touch screen has replaced button switches as a user input device in order to provide light weight and thin profile to household appliances and electronic devices. The touch screen includes a plurality of touch sensors and is mounted on a display panel of a display element. Recently, the touch screen embedded in the display panel has been developed.
Capacitive touch sensors may be generally implemented using a mutual capacitance manner. The capacitive touch sensors include mutual capacitances formed at crossings of signal lines of the display panel. When the user's finger approaches the mutual capacitance of the capacitive touch sensors, an electric field between electrodes is blocked, and a charge amount of the mutual capacitance decreases. Hence, the capacitive touch sensors may measure changes in the charge amount of the mutual capacitance before and after a touch operation and thus may recognize the touch operation.
The touch sensors of the touch screen may be coupled with one another through signal lines of a pixel array of the display panel and a parasitic capacitance. In this instance, pixel driving signals supplied to the signal lines connected to the pixels of the display panel may adversely affect the output signals of the touch sensors. Thus, a method for reducing an influence of the pixel driving signals operating as a noise component on the output signals of the touch sensors is necessary. The signal lines of the pixel array include data lines to which a video data voltage to charge the pixels is supplied, scan lines (or gate lines) crossing the data lines and to which a scan pulse (or a gate pulse) for selecting the pixels charged to the video data voltage is supplied, etc. The pixel driving signals include the video data voltage, the scan pulse, etc.
To reduce the influence of the pixel driving signals on the output signals of the touch sensors, one frame period may be divided into a display period and a touch sensor driving period, and the touch screen and the pixel array may be driven in a time division manner. During the display period, the pixel driving signals are supplied to the signal lines of the pixel array, and the video data voltage is applied to the pixels of the pixel array. During the touch sensor driving period, the pixels of the pixel array are held at the video data voltage to which the pixels have been charged during the display period, and a Tx pulse is supplied to the touch sensors to read out an output of the touch sensors. Because the touch sensor driving period is separated from the display period in terms of time, an influence of a pixel driving signals may be minimized or excluded from the output signals of the touch sensors. However, when one frame period is divided into the display period and the touch sensor driving period, if the touch sensor driving period lengthens, the display period may be relatively shortened. On the contrary, if the display period lengthens, the touch sensor driving period may be shortened. Thus, it is difficult to cope with changes in a driving method and an increase in a resolution of the pixel array or the touch screen using the time-division driving method.